Refrigerator humidity control



Dec. 12, 1961 G. MUFFLY 3,012,412

I REFRIGERATOR HUMIDITY CONTROL Filed 001;. 9, 1957 1 INVENTOR. 61 5/1 M0973 BY E1. 47 65 firm/ 6.

United States Patent 3,012,412 REFRIGERATOR HUMIDITY CONTROL GlennMuflly, 1541 Crestview Drive, Springfield, Ohio Filed Oct. 9, 1957, Ser.No. 689,151 Claims. (Cl. 62-176) This invention has to do with thecontrol of humidity in confined spaces and particularly in food storagecompartments of refrigerators. The present practice of automaticallydefrosting the cooling surfaces of non-freezing food spaces tends toincrease the average humidity in such spaces. This humidity is stillhigher when the air is cooled by non-frosting surfaces or when doors areopened frequently, particularly in southern or coastal regions where thekitchen air is very high in humidity. Because of weather changes,climate difierences and variations in door openings and other usagethere is no fixed formula, such as a constant cooling surfacetemperature, which will provide uniform humidity, hence it is founddesirable to provide means for offsetting these variations.

A main object of this invention is to provide controlled recirculationof a portion of the air over the cooling surfaces to remove additionalWater vapor from such air as required to maintain a desired averagehumidity in the food storage space.

Another object is to vary the rate of air circulation over the coolingsurfaces in order to hold its humidity within desired limits.

A further object is to vary the temperature of the cooling surfaces tovary the amount of moisture condensed from the air for the purpose ofmaintaining the moisture content of the air within desired limits.

An additional object is to select for recirculation a portion of the airwhich is warmer and/or higher in humidity.

Still another object is to employ a fan or blower both for circulatingthe air and for separating a portion of lesser density to berecirculated.

A still further object is to provide in a multiple zone refrigerator forselective removal of water vapor from the air supplied to a certain oneof said zones.

In the drawings:

FIGURE 1 is a broken sectional view of a refrigerator showing thecooling element, air circulating means and controls. 7

FIGURE 2 is another view of the air circulating and flow modifyingmeans.

FIGURE 3 is a diagrammatic view showing how the same principles may beemployed in a multiple zone refrigerator.

Referring to FIG. 1 the centrifugal blower 10, driven by shaft 12 andhaving vanes 14, is located in casing 16. Cold air taken in at thecentral port 18 is delivered via duct 20 to the refrigerated space. Aportion of the air is diverted by the damper 22 to how through therecirculation duct 24. Due to the centrifugal effect of I tor.

On the other hand any water carried by the air in the form of dropletswill by the same centrifugal effect be thrown against the inner wall ofcasing 16 and enter the trap 26, from which liquid water drains throughtube 28 to a suitable disposal means. In this way the air which flowsthrough the duct 20 is the drier and colder portion.

3,012,412 Patented Dec. 12, 19 61 ice The diverted air flowing throughduct 24 passes again over the evaporator 30 and its fins to be furthercooled and thereby to lose more of its water vapor. The evaporatorhousing 32 directs all air over the evaporator 30 and back to the blowerinlet 18 regardless of whether it was diverted through duct 24 orreturned from the refrigerated space at opening 33.

In order to control the proportion of air diverted by 22 to duct 24, Ihave provided the humidistat 34 in the refrigerated space 36 of thecabinet. When the humidity in space 36 rises the humidistat moves thevane 22 to divert more air to duct 24, whereby the humidity of space 36is brought back to normal. In some designs it may be preferred to use afixed opening at 22 and regulate the air flow through 24 by means of adamper such as 38, in which case the humidistat will be connected toactuate this damper in place of actuating thevane 22.

FIGURE 2 shows the motor 40 which is hidden in FIG. 1, but can beidentified by its shaft 12. FIGURE 2 also shows the outlet 20 at thebottom of casing 16 instead of at the top. In FIG. 2 the force ofgravity is added to centrifugal force, making a small gain in theseparation of moisture from the air, but the choice between the twoarrangements will be mainly on convenience of location of drain tube 28and the ducts 20 and 24. FIGURE 2 shows damper 38 controlled by 34',which is either the humidistat or a relay actuated thereby, as suits thecabinet design. It will be understood that this is optional in any ofthe figures. Likewise the duct 24 may leave casing 16 tangentially as inFIG. 1 or at one side as in 'FIG. 2, whichever fits best into the designof the cabinet.

The location of the side outlet to 24 in FIG. 2 has an additional effecttending to separate a lighter portion of the air for recirculation overthe evaporator. A similar effect can be obtained at any bend of conduit20, where the denser air and water vapor mixture Will tend to follow thegreater radius and the air mixture making the sharper bend will be thewarmer and wetter mixture of which a portion is diverted to the conduit24.

FIGURE 3 shows how the apparatus of FIGS. 1 0r 2 may be connected toregulate humidity in one or both compartments of a two-zonerefrigerator. It also shows an axial flow fan 10 in place of thecentrifugal fan 10 of FIGSl and 2. Either type of fan causes somecentrifugal separation of the air stream due to the whirling effect andmay be used in any of the figures. As will be seen from FIG. 3, the oneevaporator and fan may be used to cool two separate compartments fromwhich air returns to housing 32 at ports '33 and 33"instead of at a'single port 33, as in FIG. 1. The selection of which space (such as mainfood space or freezer) is to be cooled is made, by the switch 42, whichis preferably operated thermostatically to close the left-hand contactwhen the main food space 36 is to be cooled and the righthand contactwhen the freezer is to be cooled.- A temperautre rise of the left-hand(freezer) bulb 52' closes the right-hand contact and of the right-hand(main food space) bulb closes the left-hand contact. These bulbs may bein their respective compartments or in the air ducts connected withthem. 7

Assuming now that the thermostatic switch 42 is moved to the left inresponse to a rise of temperature of bulb 36 in the mainfood'compartment 36, this energizes motor 40 but does not move damper 44since solenoid 46 is not energized. It does start the condensing unit 47by energizing the relay switch 48, thus evaporator 30 is cooled andmotor-40 drives fan 10' at. full speed, delivering cooled air throughduct 50 which goes to the main food space 36 while return air entershousing 32 at 33'.

As in FIGS. 1 and 2, duct 24 bypasses a lighter (warmer and/or morehumid) fraction of the air to housing 32 under control of damper 38 forfurther cooling and dehumidificationf The damper 38 may be assumed torest in its closed position when relay 34' is not energized and to beopened as the humidity increases at the humidity-responsive device 51 todivert air through. duct v24 for further removal of water vapor byrecooling.

Assuming now that the air temperature of freezer 52 rises' 'to the pointat which the left-hand bulb 52' of switch 42 causes the switch to closethe right-hand contact, current flows through solenoid 46 in series withmotor 40, causing damper 44 to move to position 44' and motor 40 tooperate at reduced speed. The relay 48, being designed to operate ateither full or reduced voltage, starts the motor of condensing unit 47,which operates at full line voltage. Because of the lower air velocityover evaporator 30 the air now flowing to fan 19"will be colder'andlower in absolute humidity than when cooling thewarmer main-foodcompartment 36 to which air is delivered through ductf'50. Thesecompartments are indicated in FIG. 3,'as 36 and 52-, being separated bythe insulated wall 54.

The'liquid control assembly 55 comprises a receiver 56, a solenoid valve57, a main rest-rictor58 and 'a bypass restrictor 59. During normalcooling of evaporator 30, with air directed to the non-freezingcompartment 36, liquid refrigerant flows from receiver 56 through theopen'valve 57 and restrictor 58 to evaporator 30. When switch 42 movesto its right-hand position, energizing solenoid 46 and thereby movingdamper 44 to position 44 the mercury switch 60 closes its right-handcontact to energize solenoid valve 57, thereby closing it, which causesliquid to collect in 56 until it reaches'the level of outlet to 59, Withthis liquid trapped in 56 the evaporator 30 operates with less liquid init and therefore at a low- ,er temperature with evaporation occurring inless of its length.. Thus evaporator 30 is operated at a relatively hightemperature and full capacity while cooling the wmmer compartment 36 butat a lower temperature and capacity while cooling the freezercompartment 52'to which air is delivered'through duct 62.

The valve 57 is'further arranged to be closed when energized by theclosing of contact in humidistat 51, which is located as shown in duct50, in compartment 36 or in A duct 33 leading from 36. This humidistatic switch 51 closes in response to a rise of humidity of air flowingthrough compartment 36 and causes solenoid valve 57 to close, thusreducing the operating temperature of evaporator 30 to condense moremoisture from the air being included in it an additional flowrestricting means which,

when energized, reduces the liquid flow so that the evaporating pressureis right for cooling the freezer'52. The device may be identical withvalve 57 plus a restricted by-pass such as a weighted check valve or acapillary tube such as 59.

Another optional arrangement is to employ a solenoid acting directly onthe expansion valve in the direction of restricting its opening orurging it in a closing direction. A direct mechanical connection between51 and the expansion valve may be employed, omitting theelectrical'connection, if the design allows these parts to be placedcloser together. For instance. the humidity responsive element of 51 maybe a material, such as wood, which expands in response to a rise ofhumidity and acts to urge, the expansion valve in its closing directlonto reduce the evaporator pressure. This would be an expansion valveoperating much like the thermostatic type but restricting flow inresponse to a rise of humidity of air instead of the usual response to adrop of temperature at the evaporator outlet.

When solenoid 46 is energized by movement of switch 42 to the right thedamper 44 moves to position 44 and mercuryswitch 60 closes the contactbetween its middle and right-hand terminals, thus energizing 57 to causeevaporator 30 to operate at its lower temperature, regardless of Whetheror not humidistat 51 has closed its contacts. At the same time theleft-hand terminal of 60 is disconnected from the middle one causing 34'to be deenergized, allowing damper 38 to close. Ai-r flow is now throughduct 62 to the freezer compartment 52.

Due to solenoid 46-now being in series with motor 40 the speed of fan 10is reduced as is theair flow through evaporator 30. With the airvelocity thus reduced there will be less by-passing of air through duct24 even though damper 38 may be allowed to remain open. Normally theeffect of the position of damper 38 may be neglected while cooling thefreezer, but the designer may arrange the damper 38 to assume eitheropen or closed position, or to be actuated in response to changes offreezer humidity while damper 44 is in the position 44'.

supplied to compartment 36. Under this condition the latent heat removedfrom air by 30 is increased and the amount of specific heat whichit'removes is reduced to bringthe relative humidity of compartment 36down to the desired maximum.

It'is thus seen that the one evaporator 30 serves selectively to coolthe freezer 52 while operating at a low temperature, to cool compartment36 while operating at a higher temperature, and on occasions of highhumidity to cool compartment 36 while operating at a low temperature;Since bulbs 36 and 52 oppose each other in operating switch 42 thecooling effect of the one evaporator 30 is directed to whichevercompartment 36 or 52 is in the greater need of refrigeration. After thecompartment being cooled is reduced to the temperature at which switch42 opens the contact for that compartment the switch immediately closesits other contact in case the other compartment is calling forrefrigeration.

The above descriptioncovers the use of liquid control assembly 55 which,as shown, feeds liquid directly to evaporator 30. This is one of severalarrangements from which the designer may choose for the purpose ofcansing evaporator 30 to operate at high and low temperatures asrequired. One alternative is to employ an expansion valve, which is fedwith liquid from receiver 56; This valve operates normally to feedevaporator 30 at a proper pressure for cooling compartment 36 but hasWhen a single evaporator is used, as shown by 30, it is immaterialwhether or not there are two duct openings 33' and 33" into housing 32,as the return air'ducts from the two refrigerated spaces may join toenter 32 at 33 as in FIG. 1. It will be apparent that in some designsthere may be two evaporator-s 30 and/or-fans 10 or 10'. 'It will also beapparent that with one fan the'warmer evaporator of a two-temperaturesystem may be located in the return air duct leading to opening 33' andthe freezer evaporator in the 'duct leading to 33". Also there may betwo fans 10 or 10' or one of each type with one or two bypasses 24-anddampers 22 or 38. With separate fans or blowers, one delivering air toduct 50 and the other to duct 62 the damper 44 and solenoid 46 may beomitted, whether one or two evaporators are employed. Also each fan willbe of the right capacity for its job and neither fan motor will need thetwo-speed feature. No showing of a two-temperature system is deemednecessary herein as many such systems are known, including those shownin US. Patents 2,359,780; 2,375,319; 2,425, 634; 2,540,343; 2,641,109;2,695,502; 2,709,343 and 2,765,633 issued to the present applicant, withmore applications'pending. r

The switch 66 is assumed to have remained in its fullline positionthroughout the foregoing description. It is operated periodically by anyof the known methods (manuaL'elapsed time, running time, temperature,frost thickness etc.) to cause defrosting of evaporator 30 or the colderevaporator. of a two-temperature system. The device 68 is energized whenswitch 66 is moved by any of the known defrost control methods to makeits bottom contact. This movement of switch 66 breaks the circuitthrough relay 48, hence neither the fan 10' nor the condensing unit 47operates while'defrost device 68 is energized, as shown in FIG. 3,however incertain defrost methods the condensing unit may be operated,in which case the device 68 will close the compressor motor circuit ofcondensing unit 47. In most such cases the fan motor 40 will be idleduring the defrost, but where there are two fans and fan motors and atwo-temperature system with hot gas or reverse cycle defrost isemployed, one evaporator may be cooled and its fan kept running whilethe other (colder) evaporator is defrosted. Such might be the case in asystem as shown in US. application Serial Number 247,239 filed September19, 1951, by the present applicant. I

The device 68 represents any known type of defrosting system. Thecurrent supplied to it may actuate a valve for hot refrigerant (gas orliquid) defrost, be used to' heat the evaporator by the electricresistance method, start and operate the system as a heat pump todefrost the evaporator, move a damper, door, drawer, evaporator, baffle,etc., or do anything required to actuate any sort of defrosting deviceby any known method.

No matter what defrosting method is employed, some means must beprovided for the disposal of the resulting water of meltage. The drain70 may connect with any suitable container or water disposal device,preferably one which re-evaporates the drip water to ambient air.

This method of centrifugal separation of an air stream normally employslower air velocities and pressures than are used in the Hilsch, Ranqueor Vortex tube devices. It is preferred to employ the lower velocitiesproduced by normal fans for economy reasons and to avoid undue noise,making no attempt to obtain a cooling effect by the dense air method ofcompression and expansion. It is, however, the scope of this inventionto employ such higher air velocities and pressures with suitable changesof porting where this can be done with reasonable efliciency and withoutundue noise.

It will be understood that the humidity-responsive element 51 mayoptionally be located in any of several positions, where it is exposedto the air in the food storage space, air flowing toward the space orair flowing from the space. The humidistat 34, element 51 or 34' will beprovided with suitable adjustment means whereby the user may set it tohold the humidity of the storage space air within desired limits.

As used herein the term humidity generally refers to the relativehumidity of air, but it is understood that the humidity-responsiveelement 34, 34' or 51 may respond to wet-bulb temperature, dew point,absolute humidity, etc., according to the designers choice andpreference for control elements.

Optionally the switch 60 may be connected to hold damper 38 open whileair flow is directed to duct 62 whereby the full flow of by-pass airthrough duct 24 is maintained while the freezer is being cooled, thusproviding further for delivering colder air to the freezer.

This method of humidity control is not to be confused with the by-pass,recirculation or reheat methods, used in air conditioning for humancomfort. These older systems recirculate some of the warmer return airfrom the cooled space back to the cooled space, whereas in the presentinvention it is a part of the freshly cooled air which is recirculated asecond time over the evaporator. In the reheat method, as the nameindicates, air which has been cooled to a lower temperature than desiredis actually heated before delivery to the conditioned space, whereas thepresent method is one of re-cooling.

I claim:

1. In a refrigerator having two storage compartments, a refrigeratingsystem including an air cooling element, air-circulating means formoving air into heat exchange with said element and to one or the otherof said compartments, air flow directing means for selectively guidingthe flow of air to one at a time of said compartments, and air flowvelocity modifying means made effective during delivery of air to onecompartment for increasing the duration of said heat exchange andthereby the cooling and dehumidifying effect to which said air issubjected, thus delivering colder and drier air to said one compartment.

2. In a refrigerator, a food storage compartment adapted to bemaintained within a range of temperatures above 32 F., a secondcompartment adapted to be maintained within a range of temperaturesbelow 32 F., a refrigerating system, an evaporator forming a part ofsaid system, air circulating means for moving air into heat exchangewith said evaporator and through one of said compartments, air flowdiverting means whereby the air after heat exchange with said evaporatoris directed to the other of said compartments, a bypass for returning aless dense part of the air leaving said evaporator to flow in heatexchange with the evaporator a sec 0nd time, and a control responsive toan air condition of one of said compartments for regulating the flow ofair through said bypass.

3. In a refrigerator-freezer cabinet, a non-freezing storagecompartment, a frozen food storage compartment, a refrigerating systemincluding an evaporator operative selectively at low or mediumtemperatures, air flow means for causing circulation of air over saidevaporator, means for directing air circulation from said evaporatorexclusively to the non-freezing storage compartment of said cabinetwhile the evaporator is operating at a medium temperature and fordirecting air circulation from said evaporator exclusively to frozenfood storage compartment of said cabinet while the evaporator isoperating at a low temperature, the whole being operable to maintain alower absolute humidity in the frozen food compartment than in thenon-freezing compartment.

4. In combination with a refrigerator having a freezer compartment and anon-freezing food storage compartmerit, a refrigerating system includingan evaporator, power means for circulating air over said evaporator andselectively to one or the other of said compartments at a time,temperature-responsive means for selecting the compartment to which airis delivered, and means for modifying the rate of air circulation tomove air more slowly over said evaporator while it is being delivered tothe freezer compartment.

5. In a refrigerator having two food storage compartments, arefrigerating system employing a volatile refrigerant in a singleevaporator for cooling said compartments, one of said compartments beinga freezer maintained below freezing and the other a food compartmentmaintained above freezing, power-operated means for circulating air oversaid evaporator, flow controlling means whereby the major flow of saidair is selectively directed through one or the other of saidcompartments and back into heat exchange with said evaporator, bypassmeans for recirculating a wetter portion of said air to be cooled againby the evaporator before delivery to a compartment, thermostatic meansfor regulating said system and flow controlling means in accordance withthe respective needs of said compartments to hold each of them withinits pre-selected temperature limits, and control means responsive tovariations of humidity of air supplied to one of said compartments forregulating the operating temperature of said evaporator and saidby-pass, whereby the humidity of air in the last said compartment isregulated.

6. In a refrigerator having two storage compartments including one forsub-freezing storage and one for abovefreezing storage, a refrigeratingsystem including a single evaporator for cooling said compartments, airduct means connecting said evaporator with both said compartments,damper means for selectively closing the air ducts leading to saidcompartments one at a time to cool the other compartment, motor-operatedmeans for circulating air through said duct means, and control means forreducing the rate of air circulation over said evaporator while air isdelivered to one of said compartments with respect to the rate at whichair is circulated over it while delivered to the other compartment. v

7. In a refrigerator including a refrigerating system, a freezingcompartment for frozen foods, a warmer compartment for non-frozen foods,an evaporator vfor cooling air for said compartments, a fan forcirculating air in heat exchange withsaid evaporator and selectivelythrough one only of said compartments at a time to cool it, a humidityresponsive device located in the path of air circulated through saidwarmer compartment, a control device for modifying the operatingtemperature of said evaporator, means connecting said humidityresponsive device with said control device to regulate the humidity ofair in said warmer compartment, and control means responsive totemperature changes of said compartments to select the compartment to becooled, said control means including means for causing said evaporatorto cool air to a lower temperature for said freezing compartment than itnormally cools the air for said warmer compartment. 7

8. In an air treating apparatus, a fan, a housing for said fan,'an inletto said housing for air and Water vapor mix.- ture, an outlet irom saidhousing for treated air and Water vapor mixture, a second outlet leadingfrom said housing, means for collecting a less dense portion of themixture leaving said fan and delivering it to said second outlet, andmeans responsive to, changes of humidity of air discharged through thefirst said outlet for regulating the flow of air through said secondoutlet.

9. In an air treating apparatus, a fan, a housing for said fan, an inletto said housing for air and water vapor mix tnre, an outlet from saidhousing for treated air and water vapor mixture, a second outlet leadingfrom said housing, means for collecting a less dense portion of themixture leaving said fan and delivering it to said second outlet, meansresponsive to changes of humidity of air discharged through the firstsaid outlet for regulating the flow of air through said second outlet,and means for draining from said apparatus all Water separated thereinfrom said air and Water vapor mixture.

10. In a refrigerator having freezing and non-freezing compartments, arefrigerating system including evaporator means for cooling air for saidcompartments as required to maintain a suitable temperature in each, airflow control means for selectively directing air over at least a portionof said evaporator means and thence to one or the other of saidcompartments, and means for modifying the flow of air relative to saidevaporator means in response to changes of humidity in one of saidcompartments for the purpose of selecting and recooling a more humidportion of the air before it is delivered to said one of thecompartments.

References Cited in the file of this patent UNITED STATES PATENTS1,737,040 Bulkley et a1 Nov. 26, 1929 2,107,268 Averyet a1 Feb. 8, 19382,133,334 Rosett Oct. 18, 1938 2,166,813 Gibson July 18, 1939 12,236,190Wolfert Mar. 25, 1941 2,685,433 Wintermann Aug. 3, 1954 2,763,982 DegaSept. 25, 1956 2,773,356 Coblentz Dec. 11, 1956 2,783,623 Dodge d Mar.5, 1957 2,812,642 1957 Jacobs Nov. 12,

